Notice of relevant technical regulations on design and construction
All railway bureaus, investment companies and railway companies (groups to be formed):
In order to further strengthen the technical measures for the design and construction of railway tunnels under weak surrounding rocks and unfavorable geological conditions, and ensure the construction safety of railway tunnels under weak surrounding rocks and unfavorable geological conditions, in view of the outstanding problems existing in the current tunnel construction, the following technical regulations are put forward for the design and construction of railway tunnels under weak surrounding rocks and unfavorable geological conditions, which should be carefully implemented. Prior to the relevant provisions and norms in conflict with these Provisions, these Provisions shall prevail.
I. Dong Tian Project
1. The principle of "early entry and late exit" should be strictly implemented at the tunnel entrance. Strengthen the design of advance support and slope protection of tunnel section, and the entrance section of shallow tunnel should adopt open excavation or semi-bright and semi-dark way to enter the tunnel.
2. The upward slope of the tunnel entrance should be excavated and supported layer by layer from top to bottom, and the reinforcement, protection and waterproof and drainage works of the tunnel entrance should be completed in time.
3. The tunnel entrance should be supported in advance according to the design before the main tunnel construction can begin. The mouth of the cave should form a closed structure in time, and long steps are strictly prohibited.
Second, the advanced geological forecast
4. In the construction drawing stage, weak surrounding rock and unfavorable geological tunnel are assessed as high risk and extremely high risk. The design unit is responsible for the geological advance forecast, and the design unit is responsible for the organization and implementation of the geological advance forecast. The main unit responsible for the advanced geological forecast of other tunnels is the construction unit, and the advanced geological forecast is implemented by the professionals of the construction unit.
5. For karst and water-rich fractured fault tunnels, the comprehensive method of horizontal drilling should be adopted for advanced geological prediction.
6. The weak surrounding rock and tunnel with bad geological conditions shall be designed by the design unit for special advanced geological forecast, and timely collect and analyze the forecast data, improve the design scheme and guide the construction.
Third, the tunnel excavation
7. Controlled blasting or non-blasting methods should be adopted in the construction and excavation of surrounding rock sections, shallow tunnels, tunnels and adjacent existing lines of tunnels.
8. The following requirements shall be met when the step method is used in the construction of the IV, V and VI grade sections of soft surrounding rock tunnel:
(1) The supporting footage of each cycle excavation of the upper steps, the surrounding rocks of Grade V and VI shall not be greater than 1 steel frame spacing, and the surrounding rocks of Grade IV shall not be greater than 2 steel frame spacing.
(2) The footage of side wall excavation per cycle support shall not be greater than 2.
(3) Before the inverted arch excavation, the steel frame lock foot anchor must be completed, and the excavation footage shall not be greater than 3m.
(4) After the tunnel excavation, the initial support shall be constructed in time and closed into a ring, and the closed position of surrounding rocks of Grade IV, V and VI shall not be more than 35m away from the working face.
Fourth, initial support.
9. When the bench method is used in the double-track IV and V surrounding rock tunnels, measures to control the displacement of arch (wall) feet, such as locking bolts (pipes), must be set. When the double-track Ⅴ-level surrounding rock tunnel is constructed by step method, the lateral temporary support or inverted arch should be set when it is near, and the temporary support should be made of steel. 1:
10. The initial supporting steel frame shall be manufactured in the factory, and must be inspected (assembled) before leaving the factory. When the grid steel arch is adopted, the splayed grid arch should be adopted.
1 1. Wet shotcrete technology should be adopted, and it can be designed independently under special geological conditions.
V (Monitoring and measurement)
12. The tunnel monitoring and measurement shall be based on the current Technical Specification for Monitoring and Measurement of Railway Tunnels (TB 102 1-⒛07) to establish the system of grade management, information feedback and reporting. 13。 Tunnel monitoring and measurement should be included in the site construction organization as a key process. Must be equipped with full-time personnel to monitor and measure, and after training. Third-party monitoring should be implemented for urban railway tunnels that may have a serious impact on surrounding buildings.
14. Cross-section spacing of tunnel vault subsidence and clearance change measurement: Class IV surrounding rock is not more than 10m, and Class V surrounding rock is not more than 5m.
15. When the tunnel is buried under a building, a monitoring network must be laid on the surface and monitored.
16. When the vault sinks, the horizontal convergence speed reaches 5mm/d or the cumulative displacement reaches 100mm, the excavation should be suspended, and the reasons should be analyzed in time and treatment measures should be taken.
7。 When contact measurement is adopted, the hook of the measuring point should be made into a closed triangle to ensure firm deformation.
Sixth, secondary lining
18。 Railway tunnels with weak surrounding rocks and unfavorable geological conditions should be constructed with secondary lining in time. The distance between the secondary lining and the tunnel face: the surrounding rock of Grade IV should not be greater than 90m, and the surrounding rock of Grade V and VI should not be greater than 70m.